Many cardiovascular surgical procedures require that the patient's blood flow be diverted from a vein or artery to a blood treating or flow supporting device. Infusion of particular solutions or liquids into the patient's vascular system is essential to the success of many important cardiovascular procedures. Techniques and methods of using cannulas of many sizes and materials are well known in the art.
In spite of the many years of use of cannulas in surgery and the hundreds of cannula connectors and fittings, the problem of having readily at hand cannulas of the proper size to interconnect with each other, to permit a change in the size of the cannula and to permit the cannula to be introduced into and retained by a blood vessel remains. It is common to provide a cannula fitting which has one or more tapered ridges of the same diameter proximate the end of and extending from the surface of the cannula for being inserted into another cannula. A cannula fitting of this type is illustrated in, for example, U.S. Pat. No. 4,883,455 to Leonard, Nov. 28, 1989. Another type of cannula connector that comprises a double-tapered enlargement is shown in U.S. Pat. No. 4,323,072 to Rosenbluth et. al., Apr. 6, 1982. For many applications, no special structure is required to form a liquid-tight seal of adequate strength between cannulas or between valves other devices and cannulas. For example, U.S. Pat. No. 5,084,031 to Todd, et. al., Jan. 28, 1992, discloses a device in which a plane right cylindrical tube is used to connect a valving device to a cannula. This is entirely satisfactory in many applications--provided the tube on the valve is of the proper size to mate with the cannula to form a liquid tight seal of adequate strength. Therein, however, lies the problem.
It is not economically feasible to manufacture a series of complex or expensive devices which differ only as to outlet or inlet tube size. Even if such devices could be manufactured economically, having a full array of different sized devices in the operating room conveniently accessible to the surgeon is not practicable.
Frequently, the surgeon needs to shunt blood or fluid flow from one size vessel to a different size vessel. While special fittings can be, and are, available, the need to anticipate the need for various sizes and to have them on hand in the operating room is an added complexity.
It is to this problem that the present invention is addressed.